Urocanic acid, first discovered in dog urine in 1874 by Jaffe and later confirmed to occur also in human urine and epidermis, is a compound of the following formula (II). ##STR2##
Urocanic acid is thought to act as an ultraviolet absorbent and thus serve to protect the slin. Urocanic acid is also reported to have a suppressive effect on delayed allergy [The Allergy In Practice, 15(9):1995]. In addition, urocanic acid bound by ascorbic acid (Japanese Laid-Open Patent Application No. S56-161314) and thiol urocanic acid (Japanese Laid-Open Patent Application No. S60-16907) are known to have a skin brightening effect.
With its antiallergic effect, however, urocanic acid has its own shortcomings that it is only poorly soluble in water and organic solvents, thereby maling itself hard to be formulated into pharmaceutical preparations, and that its suppressive effect on delayed allergy is by no means satisfactory.
Upon the above background, the present inventors investigated to obtain urocanic acid derivatives that have sufficient solubility in water or organic solvents and having potent antiallergic effects. As a result, certain urocanic acid derivatives were found to have potent antiallergic effects and, at the same time, sufficient solubility in water or organic solvents. The present inventors completed the present invention through further investigation based on this finding.
The present invention provides urocanic acid derivatives having sufficient solubility in water or organic solvents and having potent antiallergic effects.